A burial plot is what I'm thinking, not agricultural. Or maybe just a plot to build a house on. A search campaign on Adwords and Bing would be better suited for any of those. If a burial plot, if you insist on FB, target people 55 and over living in the city where this plot is. If an agricultural plot, I'm not sure, those with an interest in farming? If a lot suitable to build a house, pretty much anyone in that city with some money.